GNU bug report logs - #5950
defvaralias after defvar should be warned in runtime

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Message #60 received at 5950 <at> debbugs.gnu.org (full text, mbox):

From: Noam Postavsky <npostavs <at> gmail.com>
To: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
Cc: 5950 <at> debbugs.gnu.org, IRIE Shinsuke <irieshinsuke <at> yahoo.co.jp>,
 Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#5950: defvaralias after defvar should be warned in runtime
Date: Fri, 3 Aug 2018 16:23:22 -0400

On 2 August 2018 at 23:33, Clément Pit-Claudel <cpitclaudel <at> gmail.com> wrote:
> On 2018-08-02 13:03, Stefan Monnier wrote:
>>>> The typical failure case goes like this, user does this:
>>>>
>>>> (setq the-package-setting 'foo)
>>>> (require 'the-package)
>>>>
>>>> And the-package.el does this:
>>>>
>>>> (defvar the-package-real-setting 'bar)
>>>> ;; Oops! User's setting of `foo' is overwritten here:
>>>> (defvaralias 'the-package-setting 'the-package-real-setting)
>>>
>>> Thanks.  Should the warning be disabled when both variables are
>>> already `defvar'd, then?
>>
>> Why?  Replace `setq` with `defvar` in the above scenario and you have
>> the same problem.
>
> Do you? I thought the problem was that you were overwriting a user setting… if you change the first setq into a defvar, where's the user setting that you're overwriting?

If the user writes defvar instead of setq, it has the exact same
effect: they've set the-package-setting to foo, which will be
overwritten to bar, same as before.

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